纤维混凝土梁抗弯性能可靠性分析

发布时间：2018-05-12 10:29

  本文选题：纤维混凝土梁 + 正截面抗弯承载力　； 参考：《东北大学》2014年硕士论文

【摘要】：在混凝土基材中掺入纤维有利于提高混凝土结构的抗弯承载力、抗变形和抗裂能力。然而,随服役时间延长,纤维混凝土梁会因混凝土碳化、钢筋锈蚀和裂缝开展等原因,导致材料性能衰减,使得构件在服役过程中可能存在安全隐患,甚至尚未达到设计基准期就丧失正常使用功能。因此,有必要对纤维混凝土梁的时变可靠性进行分析。目前,关于混凝土梁时变可靠性研究大都集中于普通混凝土,由于纤维的加入使得构件内部组分的复合效应更为复杂,理论分析难度更大,故该领域研究仍处于比较匮乏的阶段。论文在混凝土结构可靠度理论的基础上,将结构抗力视为随机过程,考虑混凝土强度、截面有效尺寸、纤维增强系数及构件承载力等影响因素,推导了纤维混凝土梁正截面抗弯承载力和基于挠度控制的可靠性分析模型,并利用一次二阶矩法进行实例计算,从强度和刚度两个方面求取了纤维混凝土梁抗弯可靠性的可靠指标和随机变量灵敏度。其次,基于混凝土材料强度、钢筋截面面积、钢筋和混凝土之间粘结系数、纤维增强系数以及计算模式不定性系数等多因素影响机制,引入钢纤维影响系数,推导了钢筋钢纤维混凝土梁正截面抗弯承载力、基于裂缝宽度控制和挠度控制的时变可靠性分析模型。以10年持续荷载作用下钢筋钢纤维混凝土梁抗弯试验为基础,讨论了各随机变量的时变规律,将等效抗力法和一次二阶矩法相结合,求取了钢筋钢纤维混凝土梁的时变可靠指标和时变灵敏度。从钢筋钢纤维梁正截面抗弯承载力时变可靠性分析可知,钢纤维的最佳掺量与相关研究成果吻合；外荷载越小,可靠指标越大,抗弯承载力越大；在服役初期,可靠指标先上升后下降。从基于裂缝宽度和挠度控制的可靠性分析可知,钢纤维掺量越高,可靠指标越大,抗变形和裂缝的能力越强,与试验结果吻合；外荷载越小,可靠指标越大,抗变形和裂缝的能力越明显；在服役初期可靠指标下降明显,随服役时间延长,可靠指标下降趋于平缓,与试验数据吻合。纤维混凝土梁抗弯性能可靠性分析可用于计算整体结构的失效概率和进行动态可靠性研究,为纤维混凝土抗裂性能及弯曲韧性的提高提供理论依据；同时对结构损伤维修、加固有一定的参考价值,为充分发挥材料潜能以及开发及应用提供理论支持。
[Abstract]:The addition of fiber in concrete substrates can improve the flexural bearing capacity, deformation resistance and crack resistance of concrete structures. However, with the extension of service time, fiber reinforced concrete beams may be damaged by carbonation of concrete, corrosion of steel bars and crack development, which may lead to the attenuation of material properties, which may lead to hidden dangers of safety in the service process. Loss of normal function even before the design benchmark period has been reached. Therefore, it is necessary to analyze the time-varying reliability of fiber reinforced concrete beams. At present, most of the researches on time-varying reliability of concrete beams are focused on ordinary concrete. Due to the addition of fiber, the composite effect of internal components is more complex, and the theoretical analysis is more difficult. Therefore, the research in this field is still in a relatively scarce stage. Based on the reliability theory of concrete structure, the structural resistance is regarded as a random process, and the influence factors such as the strength of concrete, the effective size of section, the fiber reinforcement coefficient and the bearing capacity of members are considered. The flexural bearing capacity of normal section of fiber reinforced concrete beam and the reliability analysis model based on deflection control are derived. The reliability index of flexural reliability of fiber reinforced concrete beams and the sensitivity of random variables are obtained from the aspects of strength and stiffness. Secondly, based on the influence mechanism of concrete material strength, section area of steel bar, bond coefficient between reinforcement and concrete, fiber reinforcement coefficient and uncertainty coefficient of calculation mode, the influence coefficient of steel fiber is introduced. A time-varying reliability analysis model based on crack width control and deflection control is derived for the flexural bearing capacity of steel fiber reinforced concrete beams. Based on the flexural tests of steel fiber reinforced concrete beams subjected to 10 years of continuous load, the time-varying laws of each random variable are discussed, and the equivalent resistance method and the first-order second moment method are combined. The time-varying reliability index and time-varying sensitivity of reinforced steel fiber reinforced concrete beams are obtained. From the time-varying reliability analysis of flexural bearing capacity of steel fiber beam, it can be seen that the optimum content of steel fiber is in agreement with relevant research results; the smaller the external load, the greater the reliability index, the greater the flexural bearing capacity; at the beginning of service, Reliable indicators rise first and then decrease. From the reliability analysis based on crack width and deflection control, it can be seen that the higher the content of steel fiber, the greater the reliability index, the stronger the ability of resisting deformation and crack, and the smaller the external load, the greater the reliability index. The ability of resisting deformation and crack is more obvious, and the reliability index decreases obviously at the beginning of service. With the extension of service time, the decrease of reliability index tends to be gentle, which coincides with the test data. The reliability analysis of flexural behavior of fiber reinforced concrete beams can be used to calculate the failure probability of the whole structure and to study the dynamic reliability, which can provide the theoretical basis for improving the crack resistance and flexural toughness of fiber reinforced concrete. Reinforcement has certain reference value and provides theoretical support for exerting the potential of materials and developing and applying.
【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU37
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本文编号：1878258